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Open Access
Invitro propagation in ashoka : saraca asoca (Roxb.) de wilde.
(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2011) Brindha Devi, I; KAU; Sreenivasan, E
Asoka (Saraca asoca) is an important medicinal and ornamental tropical tree currently facing the threat of extinction due to overexploitation of trees occurring in forests and other natural habitats. Unscientific and destructive extraction of bark from trees has lead to acute shortage of raw bark by ayurvedic industries. Hence, the International Union for Conservation of Nature and Natural Resources (IUCN) has listed this species under ‘globally vulnerable’ category. It is also enlisted among the 36 threatened and endangered medicinal plants of India. It is considered as the sacred tree of buddhists and Hindus. Literally the term ‘asoca’ means ‘sorrow-less’ and the tree is believed to remove the grief and unhappiness. The tree has immense medicinal properties. Its bark is considered as the primary medicinal part. Due to its acute short supply compared to its demand, various development and research activities are being prioritized to conserve, utilize and improve this species. It is mainly propagated by seeds. Due to heterozygous and cross pollinated nature of the species, it never gives a true to type progeny. Therefore the present study was undertaken to standardize the technique of in vitro propagation of Saraca asoca. Standardization of suitable explants, surface sterilization procedures and culture establishment protocol, Induction of multiple shoots and Elongation of root, hardening and planting out are the major objectives of the study. Nodal segment, Internodal segment and shoot tip were the three explants tried. Various surface sterilization procedures were tried using Chloramphenicol, ethyl alcohol, 0.1% mercuric chloride and combination of ethyl alcohol and mercuric chloride in various concentration and duration, using nodal segments as explant. Surface sterilization using 70% ethyl alcohol for 3 minutes followed by 0.1% mercuric chloride for minutes proved to be the best, which gave the maximum survival percentage of 80. The next part of the study was standardisation of suitable explants for culture establishment. Among the three explants, Nodal segments gave maximum response of 60 per cent in ½ MS medium with BAP 0.5mg/l. This was followed by shoot tips in the same medium, which gave 10 per cent response. Internodal segments did not respond in any of the media used. Standardisation of basal media for culture establishment was done using nodal segments as the explants. Three media supplemented with BA 0.5 mg.l-1 were tried viz. MS, Half strenght MS, Woody plant media. Among the three, ½ MS media was identified as the best basal medium followed by MS medium. No response was seen in WPM medium. Culture establishment as well as Shoot bud initiation was attempted in ½ MS and MS media with various growth regulator combinations. Maximum response of 60 per cent was obtained in ½ MS medium containing BAP 0.5 mg/l followed by 30 percent in the same medium containing BAP 1.5 mg/l. There were no response with 2,4-D. The response obtained was callusing in all cases. Induction of multiple shooting was tried in ½ MS medium supplemented with BAP, and Kn alone as well as combinations of BAP, IAA at various concentration. Here highest response of 30 per cent of single shoots was recorded in ½ MS media containing BAP 0.5 mg/l. Response was in the form of single shoot. The single shoots with a mean length of about 1.5mm after one week of growth was obtained. With BAP 2.0 mg/l, single shoots were produced in about 5% of cultures within 54 days. Effect of Kn in various concentration ranging from 0.5 to 2.0 mg/l was found to be low in shoot induction. The maximum length of shoot of about 1.6 cm was recorded in combination of BAP 0.5 mg/l and IAA0.5 mg/l. Various combinations of IAA and IBA at different concentrations were tried for rooting of in vitro shoots. However there was no response in any of the combinations tried.
Open Access
Epidemiology and management of black rot of cauliflower in plains of kerala
(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2011) Lakshmi Prasanna, S; KAU; Ravi, S
The present study “Epidemiology and management of black rot of cauliflower in plains of Kerala” was taken up at Department of Plant Pathology, College of Horticulture, Vellanikkara and Agriculture Research Station, Mannuthy during 2009-2011 with an aim to study the epidemic factors influencing the incidence, development and severity of black rot caused by Xanthomonas campestris pv. campestris in plains of Kerala and to conduct field studies on its management. The pathogen was isolated from the leaves and curds of cauliflower showing typical symptoms of the disease, on PSPA medium. The colonies of the isolate were yellow in colour, circular, slimy and smooth convex with entire margin. Studies on morphological, cultural and biochemical characters confirmed the bacteria as Xcc. Various types of viz., chlorotic lesion, V shaped lesions, vein blackening; necrosis and vascular discoloration were produced by the pathogen. The symptoms were initially localized and later became systemic and stunting of plants was noticed due to systemic infection. Progression and severity of the disease was studied by inoculating the plants at five days interval starting from 10 days after transplant (DAT) up to 60 DAT. Cauliflower plants of all age group were found to be susceptible to this disease. But, young plants were succumbing to death due to infection. As the age increased there was gradual decrease in the systemic infection. Plant mortality also decreased with the increase in age at which they got infected. Sixteen cauliflower varieties were screened for black rot disease under field conditions. The incidence, calculated as A- value (AUDPC), varied from 0.53 to 12.81. These varieties were grouped in to four categories based on the scale; 0-resistant, 0-3 moderately resistant, 3-5 moderately susceptible and >5 susceptible. Out of sixteen varieties, none was found to be resistant, eight were found to be moderately resistant, two were moderately susceptible and remaining six were susceptible. An attempt was made to formulate a score card for this disease for easy observation and which has a bearing on the yield. The actual area of infection in the leaf at 10, 25 and 40 days old plants were correlated with yield and a equation y=389.061+3.371(10 DAT)-0.986(25 DAT)-2.391(40 DAT) was obtained. Three system of score card were formulated and their relationships with the yield were re-correlated statistically and three additional equations were arrived. The equation two was comparable with the original equation and that score card can be better adopted as it showed 95 per cent similarity to the original, where scale 1 and 3 showed 77.5 and 90.1 per cent similarity respectively. An attempt was made to determine the role of weather parameters on incidence of this disease. The weather factors such as maximum temperature and sunshine hours were positively correlated prevailing to the observation on 9th day and average of 7, 8 and 9 days. Similarly average of 4, 5, 6; 5, 6, 7 and 6, 7, 8 days were positively correlated with only sunshine hours. A partial multiple regression equation is also derived for predicting the disease incidence. Such correlation studies have to be conducted for at least five years consecutively to arrive at a better prediction model. Initial in vitro evaluations were done to identify the chemicals, botanicals and bioagents to be carried to the field. Field trail showed that garlic extract 10 per cent, tetracycline 250 ppm and Pseudomonas fluorescens were best treatments against Xcc.
Open Access
Morphological and biochemical characterization of aromatic rice(Oryza Sativa L.) cultivars of Wayanad district of Kerala
(Department of Plant Breeding and Genetics, College of Horticulture,Vellanikkara, 2010) Sumalatha, T V; KAU; Elsy, C R
The present study was undertaken in the Department of Plant Breeding and Genetics and in the Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Ve!!anikkara and at RARS, Ambalavayal during 2008-2010 with an aim to characterize the aromatic rice cultivars of Wayanad district, based on morphological, nutritional and biochemical studies. Gandhakasala and Jeerakasala are two popular and traditional non-Basmati aromatic ricecultivars of Wayanaddistrict, Kerala. In Wayanad Gandhakasala is cultivated in an area of 327 ha, while Jeerakasala in 22 ha. Based on grain characters 10 samples of Gandhakasala and two samples of Jeerakasala were selected for characterization. Deepthi (WND.3) was used as check variety. Among morphological studies, qualitative characters like leaf bladepubescence, . panicle exsertion, spikelet awning, awn colour, lemma and palea pubescence and seed . . coat colour showed variation and hence these can be used as morphological markers to distinguish aromatic genotypes among themselves and with Deepthi. Straw coloured short and partial awns were the characteristic feature' of Jeer aka sa I a grains, while awns were absent i!1 Gandhakasala and Deepthi. Aromatic genotypes exhibited well exserted panicles and white seed coat colour whereas Deepthi showed moderately welIexserted . . panicles and red seed coat colour. Mean performance of aromatic genotypes indicated that ligule length, grain length, grain breadth, 1000 grain weight, days to 50 per cent heading, milling recovery and maturity days provided a good base for selection. Jeerakasala genotypes took more days to 50 per cent heading and to maturity than Gandhakasala genotypes and Deepthi . . In general Gandhakasala genotypes had lesser 1000 grain weight with a mean value of 13.78 gm compared to Jeerakasala (19;82 gm) and Deepthi (26.17 gm). High grain breadth and grain length would have added to high 1000 grain weight in Deepthi. In general aromatic genotypes have lesser milling recovery than Deepthi, indicating the need [or specially designed milling machines for maximum milling recovery. The genotype GT2 appeared to have higher total carbohydrate content of 81.87 per cent/while it Was Iow for JT12 (58. 40%). Jeerakasala genotypes exhibited low mean carbohydrate content of 61.06 per cent' compared to Gandhakasala( 69.56%) and Deepthi (71.73%). The three Gandhakasala genotypes GT3, GT9 and GT7 exhibited intermediate proteincontent, indicating their nutritional superiority. The amylose content of aromatic genotypes ranged between 17.87(GT4) and 23.07 (GT2) percent. Five aromatic genotypes GT1, GT2, GT8, GTlO and JT12 had intermediate amylose content. Since intermediate amylose rice is preferred in most of the rice growing regions of the world, these genotypes will have better preference in market. Most of aromatic genotypes under study were moderately aromatic, indicating their suitability for commercial cultivation. Biochemical characterization based on isozyme studies revealed the possibility of utilizing peroxidase polymorphism for identifying the aromatic rice genotypes especially Gandhakasala genotypes from other cultivars. Studies on esterase. polymorphism revealed the presence of EST-2 band only in Deepthi indicating its use as a biochemical marker to distinguish aromatic rice genotypes from Deepthi. Heritability and genetic gain studies indicated that selection of characters like length of sterile glumes, lOOO grain weight, grain length and peroxidase activity may be effective in crop improvement programme. Correlation and path studies revealed that grain yield could be improved by simultaneous selection for high seedling height, grain breadth, milling recovery and straw yield.
Open Access
In vitro propagation in ashoka (Saraca asoca (Roxb) de Wilde)
(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2011) Brindha, Devi I; KAU; Sreenivasan, E
Asoka (Saraca asoca) is an important medicinal and ornamental tropical tree currently facing the threat of extinction due to overexploitation of trees occurring in forests and other natural habitats. Unscientific and destructive extraction of bark from trees have lead to acute shortage of raw bark by ayurvedic industries. Hence, the International Union for Conservation of Nature and Natural Resources (IUCN) has listed this species under ‘globally vulnerable’ category. It is also enlisted among the 36 threatened and endangered medicinal plants of India. It is considered as the sacred tree of buddhists and Hindus. Literally the term ‘asoca’ means ‘ sorrow-less’ and the tree is believed to remove the grief and unhappiness. The tree has immense medicinal properties. Its bark is considered as the primary medicinal part. Due to its acute short supply compared to its demand, various development and research activities are being prioritized to conserve, utilize and improve this species. It is mainly propagated by seeds. Due to heterozygous and cross pollinated nature of the species, it never give a true to type progeny. Therefore the present study was undertaken to standardise the technique of in vitro propagation of Saraca asoca. Standardization of suitable explants, surface sterilization procedures and culture establishment protocol, Induction of multiple shoots and Elongation of root, hardening and planting out are the major objectives of the study. Nodal segment, Intemodal segment and shoot tip were the three explants tried. Various surface sterilisation procedures were tried using Chloramphenicol, ethyl alcohol , 0,1% mercuric chloride and combination of ethyl alcohol and mercuric chloride in various concentration and duration, using nodal segments as explant. Surface sterilisation using 70% ethyl alcohol for 3 minutes followed by 0.1% mercuric chloride for 5 minutes proved to be the best, which gave the maximum survival percentage of 80. The next part of the study was standardisation of suitable explants for culture establishment. Among the three explants, Nodal segments gave maximum response of 60 per cent in Vi MS medium with BAP 0.5mg/l. This was followed by shoot tips in the same medium, which gave 10 per cent response. Intemodal segments did not respond in any of the media used. Standardisation of basal media for culture establishment was done using nodal segments as the explants. Three media supplemented with BA 0.5 mg.l'1 were tried viz. MS, Half strenght MS, Woody plant media. Among the three, V2MS media was identified as the best basal medium followed by MS medium. No response was seen in WPM medium. Culture establishment as well as Shoot bud initiation was attempted in 14 MS and MS media with various growth regulator combinations. Maximum response of 60 per cent was obtained in Vi MS medium containing BAP 0.5 mg/1 followed by 30 percent in the same medium containing BAP 1.5 mg/1. There were no response with 2,4-D. The response obtained was callusing in all cases. Induction of multiple shooting was tried in V2 MS medium supplemented with BAP, and Kn alone as well as combinations of BAP, IAA at various concentration. Here highest response of 30 per cent of single shoots was recorded in V2 MS media containing BAP 0.5 mg/1. Response was in the form of single shoot. The single shoots with a mean length of about 1.5mm after one week of growth was obtained.With BAP 2.0 mg/1, single shoots were produced in about 5% of cultures within 54 days. Effect of Kn in various concentration ranging from 0.5 to 2.0 mg/1 was found to be low in shoot induction. The maximum length of shoot of about 1.6 cm was recorded in combination of BAP 0.5 mg/1 and IAA0.5 mg/1, various combinations of IAA and IBA at different concentrations were tried for rooting of in vitro shoots. However there was no response in any of the combinations tried.
Open Access
Screening of fertility restorers for cytoplasmic genic male sterile (CGMS) lines in rice (Oryza sativa L.).
(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2011) Adarsha, B; KAU; Jiji Joseph
The study entitled “Screening of fertility restorers for Cytoplasmic Genic Male Sterile (CGMS) lines in Rice (Oryza sativa L.)” was conducted in the Department of Plant Breeding and Genetics, College of Horticulture during the period 2009-11. The study envisaged evaluation of different CGMS sources and identification of potential restorers and maintainers among high yielding varieties of Kerala. Separate experiments viz., 1. Morphological evaluation of parents and 2. Development and evaluation of F1 hybrids, conducted to realize the objectives. Materials for the present study comprised of two CGMS lines viz., CMS 2A from Tamil Nadu Agricultural University, Coimbatore and IR 68897A, from Directorate of Rice Research, Hyderabad. Seven popular high yielding varieties of Kerala were used as male parents. Parental lines were raised and observations on qualitative and quantitative traits were recorded. Hybridization was done between CGMS lines and restorers in Line x Tester design. The F1 and the parents were raised and observations were recorded. The results on qualitative traits showed that the male parents Onam and Uma had well exserted panicle, semi-erect flag leaf orientation and well exserted stigma which are helpful in out crossing. None of the hybrids were found to be superior to parents with respect to yield due to increased spikelet sterility. Even though, hybrids CMS 2A x Kanchana, CMS 2A x Onam, IR 68897A x Aiswarya and IR 68897A x Uma recorded high pollen fertility none of the male lines can be considered as restorer. The varieties Aiswarya, Jyothi, Kanchana, Matta Triveni, Onam and Uma can be considered as a partial restorer for CGMS line CMS 2A. For the CGMS line IR 68897A, the male lines, Aiswarya, Jaya, Jyothi, Matta Triveni and Uma can be considered as partial restorer. Considering the pollen fertility of CGMS line CMS 2A, Jaya with 43.73 per cent pollen fertility can be considered as partial maintainer and for IR 68897A, Kanchana and Onam can be identified as a partial maintainer. However, in the hybrids CMS 2A x Uma and IR 68897A x Onam, few plants exhibited high pollen sterility per cent. These can be utilized to develop CGMS lines in the genetic background of Uma/Onam in future, through backcross breeding programme.
Open Access
Genetic variability studies for yield and fruit fly resistance in bitter gourd (Momordica charantia L)
(Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2010) Praveena, V S; KAU; Seeja, G
A study was undertaken in the Department of Plant Breeding and Genetics, College of Agriculture ,Vellayani during the period 2009-2010 to assess the genetic variability for different yield attributes and resistance to fruit fly in bitter gourd and to identify high yielding genotypes tolerant to fruit fly. To attain these objectives field and laboratory experiments were carried out simultaneously. Of the 29 genotypes evaluated IC-45341 was the early flowering and bearing type. Madhurai local was the genotype having maximum number of fruits per plant. Priya and Bharanikkavu local had maximum fruit length and girth respectively. Kanakakunnu local had maximum fruit weight and yield per plant. Kallukuthiavila local and Madhurai local were the long duration and short duration genotypes respectively. Priyanka had maximum protein content. Changanassery local -1 had maximum TSS, fruit colour and phenol content. IC- 68296 had maximum total sugars, reducing and non reducing sugars. Madhurai local had minimum incidence of fruit fly. Analysis of variance revealed significant differences for all the characters. Genotypic and phenotypic coefficients of variation were high for yield per plant, individual fruit weight, number of fruits per plant, fruit length, fruit girth, protein content, total sugars, reducing sugars, non reducing sugars, fruit colour, crude fibre content, phenol content and incidence of fruit fly. High heritability coupled with high genetic advance were noticed for all characters except days to first harvest, duration and water content which had high heritability and low genetic advance. Correlation studies revealed that out of the 13 significant phenotypic correlation coefficients of yield, twelve were positive and one was negative. Significant and positive correlations were obtained for yield with days to first male and female flower opening, days to first harvest, fruit bearing period, fruit length, fruit girth, individual fruit weight, duration, flesh thickness, incidence of fruit fly, protein content and water content. Significant negative correlations were obtained for incidence of fruit fly with phenol content and number of fruits per plant. Protein content, water content, phenol content and flesh thickness of immature, half mature and full mature fruits had significant correlation with incidence of fruit fly. Path coefficient analysis revealed high direct and positive effects of days to first male flower opening, fruit weight and duration on yield. D2 analysis grouped the 29 genotypes into seven clusters. Individual fruit weight contributed maximum to total divergence followed by flesh thickness, duration, fruit girth and protein content. High yielding genotype, Kanakakunnu local, was grouped into cluster I where as fruit fly resistant genotypes Madhurai local and Changanassery local – 1 were grouped into cluster V and VI respectively. This emphasizes scope for further improvement by selecting donor parents from these clusters. Selection indices revealed that Kanakakunnu local had maximum index value and Madhurai local had minimum index value. Kanakakunnu local, Changanassery local-1 and Madhurai local were identified as potent donors for appropriate breeding program for improving fruit yield and quality character like resistance to fruit fly. As per the techniques and rating system of Nath (1966) the percentage of fruit damage was minimum in Madhurai local and Changanassery local-1 under both natural screening and artificial screening. So these two genotypes were rated as resistant/highly resistant genotypes.
Open Access
Identification of fertility restorer gene in hybrid rice technology through marker assisted selection
(Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2011) Kosana, Abhishikth; KAU; Jayalekshmi, V G
The research project entitled “Identification of restorers for hybrid rice technology through molecular marker aided selection” was carried out in the department of Plant Breeding and Genetics ,College of Agriculture,Vellayani during the year 20010-11. The major objectives of this study was to Compare the morphological characters of the genotypes with the known restorers and to study the allelic status of the Kerala varieties with respect to SSR markers linked to Rf loci. This study also intended to assess the possibility for using Marker Assisted Selection for screening for restorers. The study was under taken in 19 rice varieties released by KAU and two restorers used in hybrid rice technology in Tamil Nadu Agricultural University. Biometrical analysis showed the varieties Aiswarya,Neeraja,Ptb2,Ptb13,Varsha,Swarna Prabha and Kanchana are having characters similar to the fertility characters of the known restorers . All the SSR markers selected in the study showed amplification in all the genotypes .The SSR markers, RM258, RM228, RM6100, RM6344 and RM171 showed polymorphism in the profile. SSR marker RM228 mapped on chromosome 10 and linked to Rf4 gene produced three alleles at the loci between 100-200 bp. SSR marker RM 258 mapped on chromosome 10 and linked to Rf -4 ,Rf 5 and Rf (u1)genes produced three alleles but only one of them was present in both the known restorers. SSR marker RM6100 mapped on chromosome 10 and linked to Rf4 gene produced three alleles.SSR marker RM171 on chromosome 10 linked to Rf 4 gene produced two alleles between 100-200bp. SSR marker RM6344 located on chromosome 7 and linked to Rf 4 locus produced three alleles between 100-200bp Among the five SSR markers tested in this study RM171 and RM 6100 showed a comparatively better performance in screening restorers. The dendrogram constructed with data from the amplification profile of different primer pairs show that the varieties Varsha and Neeraja with close similarity with Co48 and CB87R with respect to Rf locus. The dendrogram based on the fertility traits also clustered Varsha and Neeraja along with Co48 and CB87R. Ptb-10 and Aiswarya are on par with each other both were reported as maintainers. Members of these two clusters can be used to develop maintainers and restorers respectively. Most of the restorers so far reported are white kernelled and a probable linkage between white kernel colour and Rf loci was reported in this study also Neeraja which showed tight linkage with Co 48 the known restorer is a white kernelled variety. However Manupriya and Varsha which also showed close similarity with the known restorers are red kernelled varieties. Keralites are very specific in the quality of rice they consume. A red kernelled bold grain with non stickiness after cooking is preferred mostly. The red varieties Varsha and Manupriya can be tested for their restoring ability and can be used for the development of restorers with specific quality requirements of Kerala and there by superior hybrid which can break the yield plateau of the high yielding varieties can be released
Open Access
Genetic variability studies for yield and fruit fly resistance in bitter gourd(Momordica Charantia L)
(College of Agriculture, Vellayani, 2010) Praveena, V S; KAU; Seeja, G
A study was undertaken in the Department of Plant Breeding and Genetics, College of Agriculture ,Vellayani during the period 2009-2010 to assess the genetic variability for different yield attributes and resistance to fruit fly in bitter gourd and to identify high yielding genotypes tolerant to fruit fly. To attain these objectives field and laboratory experiments were carried out simultaneously. Of the 29 genotypes evaluated IC-45341 was the early flowering and bearing type. Madhurai local was the genotype having maximum number of fruits per plant. Priya and Bharanikkavu local had maximum fruit length and girth respectively. Kanakakunnu local had maximum fruit weight and yield per plant. Kallukuthiavila local and Madhurai local were the long duration and short duration genotypes respectively. Priyanka had maximum protein content. Changanassery local -1 had maximum TSS, fruit colour and phenol content. IC- 68296 had maximum total sugars, reducing and non reducing sugars. Madhurai local had minimum incidence of fruit fly. Analysis of variance revealed significant differences for all the characters. Genotypic and phenotypic coefficients of variation were high for yield per plant, individual fruit weight, number of fruits per plant, fruit length, fruit girth, protein content, total sugars, reducing sugars, non reducing sugars, fruit colour, crude fibre content, phenol content and incidence of fruit fly. High heritability coupled with high genetic advance were noticed for all characters except days to first harvest, duration and water content which had high heritability and low genetic advance.Correlation studies revealed that out of the 13 significant phenotypic correlation coefficients of yield, twelve were positive and one was negative.Significant and positive correlations were obtained for yield with days to first male and female flower opening, days to first harvest, fruit bearing period, fruit length, fruit girth, individual fruit weight, duration, flesh thickness, incidence of fruit fly, protein content and water content. Significant negative correlations were obtained for incidence of fruit fly with phenol content and number of fruits per plant. Protein content, water content, phenol content and flesh thickness of immature, half mature and full mature fruits had significant correlation with incidence of fruit fly. Path coefficient analysis revealed high direct and positive effects of days to first male flower opening, fruit weight and duration on yield.D2 analysis grouped the 29 genotypes into seven clusters. Individual fruit weight contributed maximum to total divergence followed by flesh thickness, duration, fruit girth and protein content. High yielding genotype, Kanakakunnu local, was grouped into cluster I where as fruit fly resistant genotypes Madhurai local and Changanassery local – 1 were grouped into cluster V and VI respectively. This emphasizes scope for further improvement by selecting donor parents from these clusters. Selection indices revealed that Kanakakunnu local had maximum index value and Madhurai local had minimum index value.Kanakakunnu local, Changanassery local-1 and Madhurai local were identified as potent donors for appropriate breeding program for improving fruit yield and quality character like resistance to fruit fly. As per the techniques and rating system of Nath (1966) the percentage of fruit damage was minimum in Madhurai local and Changanassery local-1 under both natural screening and artificial screening. So these two genotypes were rated as resistant/highly resistant genotypes.

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