Putrescine Increases Floral Retention, Pod Set and Seed Yield in Cold Stressed Chickpea

Chickpea (Cicer arietinum L.) is sensitive to cold stress (<8 °C) at its reproductive phase that results in flower abortion, poor pod set and thus reduced yield. Early maturing genotypes are especially more sensitive. In this crop, the metabolic causes underlying cold injury that are imperative to induce cold tolerance are not known. In the present study, the endogenous levels of putrescine (diamine), spermidine (triamine) and spermine (tetramine) were examined in early maturing chickpea genotype ICCV 96029, subjected to chilling temperatures of field (12–15/4–6 °C; average maximum and minimum temperature respectively), at flowering or early podding stage. These were compared with controls growing in warmer conditions (28/12 °C) of the glasshouse. The polyamine levels increased six to nine times because of stress. Relatively, putrescine (PUT) elevation was the highest but short-lived and its decrease appeared to match with the onset of flower and pod abscission in stressed plants. Compared with controls, chilling injury, observed as electrolyte leakage (EL), increased by 60 % while cellular respiration declined by 68 % in stressed plants. Exogenous application of 10 mm PUT to stressed plants reduced the EL by 29 % and elevated the cellular respiration by 40 %. PUT application at flowering stage resulted in increase of 30, 31, 23 and 25 % in floral retention, pod set, pod retention and fertile pods respectively. At the early podding stage, PUT treatment increased the seed yield per plant, seed number per 100 pods and individual seed weight by 50, 17 and 19 % respectively. The number of single-seeded pods per plant increased from 4.4 in stressed plants to 12.2 in PUT-treated plants while the number of double-seeded pods reduced from 6.2 to 4.3. The number of infertile pods declined from 8.2 in stressed plants to 3.1 in PUT-treated plants.     

The origin of chickpea Cicer arietinum L.

Summary Species relationship between the cultivated chickpea Cicer arietinum and the two newly discovered wild species C. echinospermum and C. reticulatum were assessed through breeding experiments and cytological examination of the hybrids.The two wild species differed from each other by a major reciprocal translocation and their hybrid was completely sterile. The wild species C. echinospermum also differed from the cultivated species by the same translocation and their hybrid was highly sterile. The other wild species, C' reticulatum, was crossed readily with the cultivated chickpea. Meiosis of the hybrids, involving 4 different C. arietinum lines, was normal, and they were fertile. This wild species therefore can be considered as the wild progenitor of the cultivated chickpea.     

Chemical Manipulation of Reproductive Efficiency of Chickpea (Cicer arietinnum L.) by Triadimefon in Relation to Changes in Ethylene

Reproductive efficiency was successfully manipulated by the application of different concentrations of triadimefon at pre‐flowering, flowering and post‐flowering stages in chickpea (Cicer arietinum L.). Triadimefon improved the parameters determining reproductive efficiency. Yield was significantly improved due to reductions in flower and pod abscission by the application of triadimefon, which also lowered the ethylene levels in leaves, flowers and pods and delayed senescence. These findings suggest a relationship between ethylene level and reproductive efficiency in chickpea. Further, they indicate that triadimefon can be used for chemical manipulation of the reproductive efficiency of chickpea under field conditions.     

Transgressive segregations for yield criteria in reciprocal interspecific crosses between <Emphasis Type="Italic">Cicer arietinum</Emphasis> L. and <Emphasis Type="Italic">C. reticulatum</Emphasis> Ladiz.

Wild Cicer species are considered to be more resistant for biotic and abiotic stresses than that of the cultivated chickpea (Cicer arietinum L.). Alien genes conferring resistance for biotic and abiotic stresses can be transferred from wild Cicer species to the cultivated chickpea but success in interspecific hybridizations has already been achieved with only two wild Cicer species. The current study was undertaken to compare fruitful heterosis in F₂ and F₃ for yield and yield criteria and to identify transgressive segregation in F₂ and F₃ in reciprocal interspecific crosses between C. arietinum and C. reticulatum Ladiz. We define fruitful heterosis as a useful parameter that can be used instead of residual heterosis. Considerable fruitful heterosis in F₂ and F₃ was found for number of seeds, pods per plant, biological yield, and seed yield. Maximum values of most of the characteristics in F₂ and F₃ were higher than that of the best parent indicating that superior progeny could be selected for yield from transgressive segregation. Progeny selection should be based on number of seeds, pods per plant, and biological yield since these characteristics had the highest direct effect on seed yield. The narrow sense heritability was found to be the highest for 100-seed weight. It was suggested that the cultivated chickpea could be used as female parent in interspecific hybridization to increase yield and yield criteria since progeny in F₂ and F₃ had better performance when it was used as female. In conclusion, interspecific hybridization of wild and cultivated chickpea can be used to improve yield and yield components and resistance to biotic and abiotic stresses as well.     

Cross compatibility between chickpea and its wild relative,Cicer echinospermum Davis

Summary Cicer echinospermum, a wild relative of chickpea (Cicer arietinum L.), has traits that can be used to improve the cultivated species. It is possible to obtain successful crosses between the two species, even though their cross progenies have reduced fertility. The reasons for this low fertility could be due to the two species differing in small chromosome segments or at genic level. Another limitation to the use ofC. echinospermum at ICRISAT Asia Center is that the species is not adapted to the short photoperiod which prevails during the chickpea cropping season at Patancheru, Andhra Pradesh, India. Future work will include screening the segregating progenies for monitoring traits from both the species through isozyme analysis and to incorporate these into good agronomic backgrounds following backcrosses.Submitted as JA 1669 by ICRISAT     

Variation in Cicer arietinum L.

Summary A collection of populations and cultivars of Cicer arietinum L. were studied to obtain phenotypic, genotypic and environmental correlation coefficients, and broad sense heritabilities. Principal Component Analyses were performed on phenotypic, genotypic and environmental matrices. Data and phase obtained on a pure morphological basis, as well as on quantitative genetic studies and geographical distribution support the existence of two complexes within the cultivated chickpea, macrosperma and microsperma. These taxa differ in a cluster of complex characters associated with seed. pod and leaf morphology, and they differ in distribution. There is no taxonomic basis to treat these as subspecies. We propose to include C. reticulatum Lad., the wild chickpea, as a subspecies of C. arietinum, with the cultivated kinds recognized as subspecies arietinum. Race macrosperma was derived from race microsperma through selection during relatively recent times of the evolutionary history of the chickpea.     

Antibiosis mechanism of resistance to pod borer, Helicoverpa armigera in wild relatives of chickpea

The pod borer, Helicoverpa armigera, is one of the major constraints to chickpea production worldwide. The levels of resistance to pod borer in the cultivated chickpea germplasm are moderate, and therefore, we studied the reaction of 32 accessions of wild relatives of chickpea for resistance to H. armigera under greenhouse conditions. Accessions ICC 17257, IG 70002, IG 70003, IG 70012, (Cicer bijugum), IG 69948 (C. pinnatifidum), IG 69979 (C. cuneatum), IG 70032, IG 70033, IG 70038, and IG 72931 (C. judaicum) showed lower leaf feeding, a drastic reduction in larval weight, and poor host suitability index at the vegetative and/or flowering stages of crop growth as compared to the cultivated chickpeas. Based on percentage pods damaged by 5th day (< 52% pods damaged compared to 90% pods damaged in Annigeri), and percentage weight gain by the larvae (< 35% weight gain compared to 366% weight gain on ICCV 2); accessions IG 69979 (C. cuneatum), IG 70003, IG 70022, IG 70016, IG 70013, IG 70012, IG 70010, IG 70001, IG 70018, and IG 70002 (C. bijugum), and IG 72953 (C. reticulatum) showed high levels of resistance to H. armigera. Larvae of H. armigera weighed < 50 mg when reared on C. pinnatifidum (IG6 9948 and IG 70039), and C. judaicum (IG 72931) compared to 301.95 mg on C. arietinum (ICCC 37 – the cultivated chickpea). Larval weights on many accessions of the wild relatives of chickpea were much lower than those on the cultivated chickpeas, indicating the existence of different mechanisms of resistance to H. armigera. There was no pupation and adult emergence when the larvae were reared on accessions of C. pinnatifidum (IG 69948 and IG 70039), and C. judaicum (IG 69980, IG 70032, IG 70033 and IG 72931). The wild relatives of chickpea showing high levels of antibiosis to H. armigera can be used to introgress diverse resistance genes into cultivated chickpea to increase the levels and diversify the basis of resistance to this insect. An erratum to this article is available at .     

Gene effects of Cicer reticulatum on qualitative and quantitative traits in the cultivated chickpea

The gene effects of Cicer reticulatum on both double‐podding as qualitative traits and yield criteria as quantitative traits in interspecific hybridization with cultivated chickpea (Cicer arietinum) have not yet been elucidated, despite the easy acquisition of hybrid progeny between two species. This study sought to answer three questions concerning qualitative and quantitative traits in reciprocal crosses between C. arietinum and C. reticulatum. (i) Is there a similarity in the gene effects of flower colour, pigmentation and double‐podded traits in reciprocal interspecific crosses? (ii) What are the expressivity and penetrance of the double‐podded trait in interspecific crosses? (iii) Which heterosis predicts the occurrence and the extent of transgressive variation? The materials for this study were F₁, F₂ and F₃ progeny derived from a reciprocal cross between C. arietinum and C. reticulatum. As qualitative traits, purple flower colour, pigmentation and single‐podded traits in C. reticulatum were governed by a dominant single gene. Purple flower colour and pigmentation were detected to be linked traits as all progeny had the same phenotypes. As quantitative traits, yield criteria in progeny which were double‐podded had higher values than the single‐podded counterparts. Expressivity and penetrance of the double‐podding trait were superior in progeny derived from C. reticulatum × C. arietinum. The results showed that fruitful heterosis was more useful than residual heterosis in F₃ as residual heterosis was mostly negative and fruitful heterosis was suggested in self‐pollinated species such as chickpea that lacks inbreeding depression. Interspecific transgression was significant with respect to chickpea improvement because it represented a potential source of novel genetic variation.     

Genetic diversity estimates in Cicer using AFLP analysis

Amplified fragment length polymorphism (AFLP) analysis was used to evaluate the genetic variation among cultivated chickpea and wild Cicer relatives. In total, 214 marker loci were assessed, of which 211 were polymorphic (98.6%) across the 95 accessions that represented 17 species of Cicer. The genetic variation within a species was highest in C. pinnatifidum followed by C. reticulatum and lowest in C. macracanthum. Three main species groups were identified by UPGMA clustering using Nei's pair‐wise distance calculations. Group I included the cultivated species C. arietinum, C. reticulatum and C. echinospermum. Within this group, C. reticulatum accessions were clustered closest to the C. arietinum cultivars ‘Lasseter’, ‘Kaniva’ and ‘Bumper’, supporting the hypothesis that C. reticulatum is the most probable progenitor of the cultivated species. Cicer bijugum, C. judaicum and C. pinnatifidum were clustered together creating group II. Group III contained all nine perennial species assessed and two annual species C. yamashitae and C. cuneatum. The genetic distance detected between group I and group III (0.13) was equivalent to the genetic distance detected between group I and group II (the primary and annual tertiary species, respectively; 0.14). This indicated that the perennial tertiary species may be as valuable for increasing variation to incorporate novel germplasm in the cultigen as the annual tertiary species.     

Old and New Cultivars of Soya Bean (Glycine max L.) Subjected to Soil Drying Differ in Abscisic Acid Accumulation,Water Relations Characteristics and Yield

Two old (Huangsedadou and Longxixiaohuangpi (LX)) and two new (Jindou 19 (JD) and Zhonghuang 30 (ZH)) soya bean (Glycine max (L.) Merr.) cultivars were used to investigate the influence of soil drying on the abscisic acid (ABA) accumulation in leaves, stomatal conductance (g_s), leaf water relations, osmotic adjustment (OA), leaf desiccation tolerance, yield and yield components. The greater ABA accumulation was induced by soil drying, which also inducing g_s decreased at higher soil water contents (SWC) and leaf relative water content (RWC) significantly decreased at lower SWC in the new soya bean cultivars than in the old soya bean cultivars. The soil water threshold between the value at which stomata began to close and the RWC began to decrease was significantly broader in the new cultivars than in the old cultivars. The new cultivars had significantly higher OA and lower lethal leaf water potential than old cultivars when the soil dried. The old cultivars had greater biomass, but lower grain yield than the new cultivars in well‐watered, moderate stress and severe stress conditions. Thus with soil drying, the new soya bean cultivars demonstrated greater adaptation to drought by inducing greater ABA accumulation, stomatal closure at higher SWC, enhanced OA and better water relations, associated with increased leaf desiccation tolerance, greater water use efficiency and higher yield.     

Leaf shape × sowing density interaction affects chickpea grain yield

Modifying plant architecture is considered a promising breeding option to enhance crop productivity. Modern chickpea (Cicer arietinum L.) cultivars with either compound (wild‐type) or simple leaf shapes are commercially grown but the relationships between leaf shape and yield are not well understood. In this study, a random sample of ‘Kabuli’ type progeny lines of both leaf types, derived from two crosses between modern American simple leaf cultivars and early‐flowering wild‐type breeding lines, were planted at different sowing densities. Leaf area development and final grain yield in genotypes of the two leaf types responded differently to changes in sowing densities. Compound leaf lines attained higher leaf area indices and higher grain yields at both low and high sowing densities. Yield responses of the simple leaf lines to increasing sowing density were significantly higher compared to compound leaf genotypes in two of three field experiments. The prospects for utilizing the simple leaf trait as a breeding target for short‐season growing areas are discussed.     

Interspecific hybridization between Cicer arietinum and C. pinnatifidum

An interspecific hybrid between Cicer arietinum cv. GL 769 and a wild species C. pinnatifidum was obtained after emasculation, pollination and application of growth regulators. Ovules were cultured and embryos were later dissected to obtain hybrid plants. These plants were albinos and morphologically resembled C. pinnatifidum. Shrivelled seeds were also obtained in 2% of the crosses, which on germination gave rise to albino plants. These plants did not survive beyond 20 days. The hybrid nature of these plants was confirmed by esterase isozyme studies. Hybrid shoots obtained from germinating embryos were cultured on modified ML-6 medium with BAP 2 mg/1, IAA 0.5 mg/1, where they turned green after 3–4 weeks. Transmission electron microscopy (TEM) studies on leaf sections from green hybrid shoots showed an improvement in the chloroplast structure, with better organized grana.     

A gene producing one to nine flowers per flowering node in chickpea

Chickpea (Cicer arietinum L.) has a racemose type of inflorescence and at each axis of the raceme usually one or two and rarely three flowers are borne. Plants producing 3 to 9 flowers, arranged in acymose inflorescence, at many axis of the raceme, were identified in F₂ of an interspecific cross ICC 5783 (C. arietinum) × ICCW 9 (C. reticulatum)in which both the parents involved were single-flowered. A spontaneous mutation in one of the two parents or in the F₁was suspected. However, the possibility for establishment of a rare recombination of two interacting recessive genes could not be ruled out. The number of pods set varied from 0 to 5 in each cyme. Inheritance studies indicated that a single recessive gene, designated cym, is responsible for cymose inflorescence. The allelic relationship of cym with sfl, a gene for double-flowered trait, was studied from a cross involving multi flowered plants and the double-flowered line ICC 4929. Thecym gene was not allelic to sfl, suggesting that two loci control the number of flowers per peduncle in chickpea. The cym locus segregated independently of the locus sfl, ifc (inhibitor of flower color) and blv (bronze leave). This revised version was published online in August 2006 with corrections to the Cover Date.     

Investigations into the Barrier(s) to Interspecific Hybridization between Cicer arietinum L. and eight other Annual Cicer species

Barrier(s) to interspecific hybridization between the cultivated chickpea, Cicer arietinum L., and eight other annual wild species, i.e. C. reticulatum Lad., C. echinospermum Dav., C. pinnatifidum J. and S., C. judaicum Boiss., C. bijugum Rech., C. chorassanicum (Bge) M. Pop., C. yamashitae Kit. and C. cuneatum Rich., were investigated. In general, good pollen germination and pollen tube growth were observed in all eight crosses and their reciprocals. En spite of a few pollen cube growth abnormalities in most crosses, pollen tube penetration into the ovule and, thus, fertilization was observed in all cross combinations. However, differences were observed in the time from pollination to fertilization, not only between different interspecific crosses but also between reciprocals of a particular interspecific cross. The crossability barrier is, therefore, believed to be due to factor(s) operating after fertilization.     

Modulation of Brassica napus source–sink physiology through film antitranspirant induced drought tolerance amelioration that is dependent on the stress magnitude

Increase in drought conditions during the oilseed rape (OSR) reproductive phase is predicted to occur more often in the temperate zone, leading to significant yield losses. Crop management solutions such as film antitranspirant (AT) applied at key drought‐sensitive growth stages on both wheat and oilseed rape have recently been shown to alleviate drought‐induced yield losses. However, there is a lack of information regarding potential AT effectiveness to reduce drought damage on OSR plants at different soil moisture regimes. Therefore, two similar experiments were performed in a computer‐controlled glasshouse/phenotyping centre to investigate the physiological responses of OSR to well‐watered (WW), moderate water stress (MWS), water stress (WS) and severe water stress (SWS) conditions. Stress treatments were imposed at the initiation of flowering and treated with an AT or water onto the leaf canopy. Stress limited the gas‐exchange and increased leaf temperature, leaf‐to‐air temperature, bud‐to‐air temperature and ABA concentrations which increased with stress intensity in all tissues analysed. Yield components were significantly reduced by WS and SWS treatments when compared to the WW plants. Application of AT counteracted the detrimental effect of WS and SWS by decreasing water use over the first few days of stress application thus improving relative water content and leaf water‐use efficiency, decreasing ABA accumulation in leaf and all the reproductive organs analysed (buds, flowers and pods) and avoiding bud‐to‐air temperature increases. AT application sustained pod formation and seed production under WS but only seed production under SWS conditions. These data suggest that leaf‐canopy application of AT at key phenological stages under particular magnitudes of soil moisture deficit may sustain OSR reproduction and reduce yield losses.     

Protective Effects of Polyamines against Oxidative Stress Induced by Water and Cold Stress in Chickpea

Chickpea (Cicer arietinum L.) yields are drastically reduced by water and cold stress that occur individually or simultaneously in northern region of India. The comparative effects of both the stresses were investigated at the metabolic level by examining the endogenous status of polyamines (PAS), active oxygen species and antioxidants. Chickpea plants (15‐day old) growing hydroponically under controlled conditions (light/ dark; 24/21 °C, 16/8 h; irradiance 250 μmol m^?2 s^?1) were subjected to water deficit stress (Ψ_s of ?0.2 to ?1.0 MPa) and cold stress (5–25 °C) for 4 days. LD₅₀ in terms of root growth rate (RGR), electrolyte leakage and triphenyl tetrazolium chloride (TTC) reduction activity was observed at ?0.6 MPa and 10 °C for water and cold stress, respectively. In a subsequent experiment, 15‐day‐old plants were exposed to these stress levels under the above‐mentioned growth conditions for 7 days and analysed for various parameters. In cold‐stressed plants (CS), putrescine (PUT) was observed to be relatively higher while water‐stressed plants (WS) had more of spermidine (SPD). Spermine (SPM) levels increased more rapidly in WS and declined on the fourth day of stress while in CS, a gradual increase occurred that decreased on the seventh day. The accumulation of PAs was short‐lived under the combined presence of both the stresses. Hydrogen peroxide elevated abruptly in WS and remained higher than CS while the latter showed a marked increase in malondialdehyde content. Ascorbic acid increased sharply in WS that decreased on the fourth day while CS showed a relatively gradual increase that reached its maximum on the fourth day and declined subsequently. Glutathione was significantly higher in CS plants in comparison with WS and CS + WS plants. The activity levels of superoxide dismutase were higher up to 4 days and declined subsequently while those of WS stayed higher till the last day of stress. Ascorbate peroxidase levels were significantly higher in CS plants while catalase activity was comparatively more in WS. Exogenous application of PAs reduced the level of hydrogen peroxide, malondialdehyde content and raised the level of antioxidants. Put caused 44 and 32 % increase in RGR in CS and WS, respectively, while SPD resulted in 110 and 25 % enhancement in WS and CS, respectively. Under combination of stresses, RGR increased by 21, 53 and 10 % by Put, SPD and SPM, respectively. The effects of PAs could be reversed largely by their biosynthetic inhibitors. α‐difluoromethylornithine (a biosynthetic inhibitor of putrescine) caused more damage to CS while cyclohexylamine (inhibitor of SPD and SPM biosynthesis) was more inhibitory in WS.     

Genetic Variation in the Ability of Detached and Partially Dehydrated Leaves of Rice to Accumulate Abscisic Acid, Measured by Radioimmunoassay

Variation in the ability o) 60 rice (Oryza saliva L.) varieties and three wild species to accumulate abscisic acid (ABA) in response to drought stress, drought-induced ABA accumulation (DIAA), was assessed using a standard detached-leaf lest. The range in DIAA amongst these genotypes was compared with the range amongst F₂ plants and F₆, lines derived from the O. saliva cross ‘IR20’ב63–83’ which were selected through several generations solely on the basis of differences in DIAA. ABA was measured by radioimmunoassay (RIA) or by gas chromatography (GC). DIAA in the 60 varieties was normally distributed with a six-fold range, from 245 to 1580 ng g^?1 FW. Wild species varied two-fold in DIAA, from 375 to 889 ng g^?1 FW. DIAA in F₂ plants from the ‘1R20’ב63–83’ cross was also normally distributed. The extremes of DIAA for the low-ABA and higb-ABA F₆ lines (330 and 1435ng g^?1 FW) were similar to those for the varieties. Measurements by RIA and GC gave similar results. These findings are discussed in the context of producing further sets of closely-related genotypes with similar leaf areas to study the association between DIAA and water-use efficiency.     

Exogenous Application of Abscisic Acid Improves Cold Tolerance in Chickpea (Cicer arietinum L.)

Chickpea suffers cold stress (<10 °C) damage especially during reproductive phase resulting in the abortion of flowers and pods, poor pod set, and reduction in seed yield and seed quality. One of the ways in modifying cold tolerance involves exogenous treatment of the plants with chemicals having established role in cold tolerance. In the present study, the chickpea plants growing under optimum temperature conditions (28/12 °C, as average maximum and minimum temperature) were subjected to cold conditions of the field (10–12/2–4 °C; day/night as average maximum and minimum temperature) at the bud stage. Prior to exposure, these plants were treated exogenously with 10 μm abscisic acid (ABA) and thereafter again after 1 week of exposure. The stress injury measured in terms of increase in electrolyte leakage, decrease in 2,3,5-triphenyl tetrazolium chloride reduction %, relative leaf water content and chlorophyll content was observed to be significantly mitigated in ABA-applied plants. A greater pollen viability, pollen germination, flower retention and pod set were noticed in ABA-treated plants compared with stressed plants. The seed yield showed considerable improvement in the plants treated with ABA relative to the stressed plants that was attributed to the increase in seed weight, greater number of single seeded pods and reduction in number of infertile pods. The oxidative damage measured as thiobarbituric acid-reactive substances was lesser in ABA-treated plants that was associated with greater activities of superoxide dismutase, catalase, ascorbate peroxidase, ascorbic acid, glutathione and proline in these plants. It was concluded that cold stress effects were partly overcome by ABA treatment because of the improvement in water status of the leaves as well as the reduction in oxidative damage.     

Variation in pod production and abortion among chickpea cultivars under terminal drought

The effect of terminal drought on the dry matter production, seed yield and its components including pod production and pod abortion was investigated in chickpea (Cicer arietinum L.). Two desi (with small, angular and dark brown seeds) and two kabuli (with large, rounded and light coloured seeds) chickpea cultivars differing in seed size were grown in a controlled-temperature greenhouse, and water stress was applied by withholding irrigation 1 (early podding water stress, ES), 2 (mid-podding water stress, MS) or 3 (late-podding water stress, LS) weeks after the commencement of pod set. In addition, the pod and seed growth of well-watered plants was followed for the first 19 days after pod set. Growth of the pod wall followed a sigmoid pattern and was faster in the desi than in the kabuli cultivars, while no difference was found in early seed growth among genotypes. Time of pod set affected the yield components in all treatments with the late-initiated pods being smaller, having fewer seeds per pod and smaller seeds, but no significant difference between pods initiated on the same day on the primary and secondary branches was observed. Early stress affected biomass and seed yield more severely than the later stresses, and in all stress treatments secondary branches were more affected than primary ones. Pod production was more affected by early stress than by late stress, regardless of cultivar. Pod abortion was more severe in the kabuli than in the desi cultivars, but final seed size per se did not appear to be a determinant of pod abortion under terminal drought conditions. The data indicated that the production and viability of pods was affected as soon as water deficits began to develop. The results show that pod abortion is one of the key traits impacting on seed yield in chickpeas exposed to terminal drought and that irrespective of differences in phenology, kabuli types have greater pod abortion than desi types when water deficits develop shortly after first pod set.     

Genotypic Variation for Tolerance to Transient Drought During the Reproductive Phase of Brassica rapa

Brassica rapa L. is a genetically diverse parent species of the allotetraploid species, oilseed rape (B. napus) and a potential source of drought tolerance for B. napus. We examined the effect of a 13‐day drought stress period during the early reproductive phase, relative to a well‐watered (WW) control, on subsequent growth and development in nine accessions of B. rapa and one accession of Brassica juncea selected for their wide morphological and genetic diversity. We measured leaf water potential, stomatal conductance, water use, and leaf and bud temperatures during the stress period and aboveground dry weight of total biomass at maturity. Dry weight of seeds and reproductive tissue were not useful measures of drought tolerance due to self‐incompatibility in B. rapa. The relative total biomass (used as the measure of drought tolerance in this study) of the 10 accessions exposed to drought stress ranged from 47 % to 117 % of the WW treatment and was negatively correlated with leaf‐to‐air and bud‐to‐air temperature difference when averaged across the 13‐day stress period. Two wild‐type (B. rapa ssp. sylvestris) accessions had higher relative total and non‐reproductive biomass at maturity and cooler leaves and buds than other types. We conclude that considerable genotypic variation for drought tolerance exists in B. rapa and cooler leaves and buds during a transient drought stress in the early reproductive phase may be a useful screening tool for drought tolerance.